Trigger mechanism for ball activated device

ABSTRACT

A trigger mechanism for a ball activated device ( 100 ) comprises a seat sleeve ( 130 ) with seat defining members ( 132 ) forming a fluid tight seal with a ball ( 300 ) in an initial state and allowing the ball ( 300 ) to pass in a final state. An alternating member ( 125 ) can move radially in an aperture ( 124 ) through an inner sleeve ( 120 ) and abuts an outer surface on the seat sleeve ( 130 ) in the initial state, is received in a recess ( 134 ) on the seat sleeve ( 130 ) in an intermediate state, and is received in a groove ( 114 ) in the outer sleeve ( 110 ) in the final state. A protective sleeve ( 150 ) may extend axially from the seat sleeve ( 130 ) over a seat receiving area ( 115 ). The mechanism is suitable for cementing and fracturing as particles cannot penetrate to its moving parts.

BACKGROUND

1. Field of the Invention

The present invention relates to well equipment for use in the oil andgas industry, in particular to a trigger mechanism for a ball activateddevice.

2. Background Art

In order to produce hydrocarbons, i.e. oil and gas, a borehole isdrilled through several layers of rock in a formation. Hydro carbons maybe present in a zone comprising a layer of porous rock under a layer ofnon-porous rock. Several such zones can be present along the borehole.The borehole may extend horizontally along one or more zones. All orpart of the borehole can be lined by a steel casing or liner cemented tothe rock to form a wellbore. One or more production strings can beinserted into the wellbore. As used herein, the term ‘tubing’ means anycasing, liner or production string having a central bore through which afluid may flow. Different tubings are provided with various devices suchas valves, loggers, plugs, packers etc. in order to complete the well orto control the production from the different zones as known in the art.

One or more injection wells can be provided in a similar manner. Aninjection well is typically used to increase the pressure in a remotepart of a zone to force the hydro carbons in the direction of aproduction well and thereby increasing the production.

The devices in the well can be operated in a number of known manners,including by so-called drop balls. A ball activated device is includedin a tubing, and comprises a ball seat which forms a fluid tightobstruction with a drop ball of a suitable size. When it is desired toactivate the device, the drop ball is dropped or pumped down within thetubing until it lands on the ball seat. Then, pressure is applied behindor upstream from the ball. When the force exerted by the pressure on thepiston area exceeds a predetermined level, the ball seat shiftsdownstream and activates the device, for example by shifting a slidingsleeve valve from a closed position to an open position. In a cementingoperation cement can then be pumped through the open valve into anannulus behind the casing, e.g. between the casing and the formation. Ina fracturing operation, fracturing fluid with suitable proppants can bepumped through the open valve.

As known in the art, any suitable object can be dropped or pumped downthe well to prevent fluid flow through a seat. The terms ‘ball’ and‘ball activated’ are used for simplicity, and the term ‘ball’ should beregarded as any object capable of blocking a flow as discussed above.

In some wells, several ball activated devices are provided with seatdiameters that decrease with the distance from the surface, which istermed the downstream direction in the present disclosure. To activatethe ‘deepest’ device, i.e. the device furthest away from the surface,the smallest of a plurality of balls is pumped down and passes all thelarger seat diameters before lodging or landing on the last seat.Thereafter, successively larger balls are used to activate the devicescloser to the surface.

For simplicity, a sliding sleeve valve is used to illustrate a ballactivated device in the following description. However, it should beunderstood that the ball activated devices considered in the presentinvention are not limited to sliding sleeve valves. For example, alinear motion is easily transformed to a rotation using helicalshoulders between two sleeves or a rack and gear arrangement. Thus, anaxially moving seat may turn an element around its axis, e.g. a ball ina ball valve or a plate in a butterfly valve.

U.S. Pat. No. 4,360,063 A (Kilgore) discloses a slide valve with a ballseat comprising lugs on collet fingers defing a ball seat. When it isdesired to close the valve, a ball is dropped into a tubing and pressureis exerted to move the ball downward and close the slide valve. When thevalve closes, the lugs expand into a groove and permit the ball to fallthrough the slide valve member. The lugs hold the slide valve in closedposition. The spaces between the lugs on the collet fingers may bedimensioned to be of close tolerance or provided with resilient materialto restrict or prevent flow therethrough and/or the ball may be made ofresilient material or have a hard core with a resilient cover to inhibitor prevent flow of fluid through the collet fingers when the ball isseated on the fingers. In this manner, one ball can lodge on severalseats, all having the same diameter, and activate corresponding valvesone by one.

In U.S. Pat. No. 4,360,063 the seat is affixed to the sliding sleeve.Thus, the force exerted on the ball and seat must be sufficient toovercome an initial retaining force keeping the sliding sleeve open plusa friction force between the entire sliding sleeve and the surfacewithin which it slides all at once. This friction force can besignificant, in particular if the slide valve has been exposed toaggressive and/or contaminated well fluids for an extended period oftime. Further, before the ball lands on the seat, particles in the wellfluids or scaling may deposit in the groove into which the lugs aresupposed to expand. If the lugs do not expand radially, the ball isprevented from passing through and the intended operation fails.

U.S. Pat. No. 8,215,401 B2 (Braekke et al.) discloses a colletconfigured to slide axially within an inner sleeve, which in turn isconfigured to slide axially within an outer sleeve. The collet compriseslongitudinal fingers. Initially the fingers form a ball seat and thecollet is retained by a first release mechanism designed to release thecollet from the inner sleeve when a first pressure exceeds apredetermined level. A second release mechanism is designed to releasethe fingers when the device is activated, e.g. when the valve hasshifted from an initially closed to a final open state. Once released,the fingers flare out in order to permit the ball to pass.

One problem with the expandable seat of U.S. 8,215,401 B2 is the needfor a second pressure greater than a first pressure in order to releasethe second release mechanism after the to first release mechanisms toensure proper operation of the device. In some applications, it might beadvantageous to activate a device once a predetermined pressure isreached, and still be guaranteed that certain steps between the initialand final states are performed in a predetermined sequence to ensureproper transition from the initial to the final state.

Further, the collet fingers in U.S. 8,215,401 B2 are preferably spacedapart such that one collet can be configured to a desired ball seatdiameter by mounting suitable lugs between the distal ends of thefingers and the surface in which the collet slides. However, inapplications where a fluid containing particles, e.g. in cementing orfracturing operations, particles such as sand or proppant may enterbetween the fingers and settle behind them such that they do not flareout to let the ball pass.

In one embodiment disclosed in U.S. Pat. No. 8,215,401 B2, the firstrelease mechanism comprises a head intended to slide over a smallstopping shoulder. This head may require a space between two sleevesinto which sand or proppant may enter. In general, particles may enterspaces between or behind sleeves and prevent proper operation of theexpandable ball seat.

In other applications, an expandable ball seat is designed to stay in aproduction string for an extended period of time before being activated.In such applications, scaling and/or corrosion may cause similarproblems. For example, scaling may build up between the sleeves or inexposed grooves and prevent the sleeve from moving axially or the ballseat from expanding radially. Corrosion may affect mechanical parts suchas exposed shear pins or helical shoulders required for transforming alinear motion into a rotation. Hence scaling and corrosion might preventproper operation of the trigger mechanism and/or the ball operateddevice triggered by the mechanism.

An object of the present invention is to solve at least one of theproblems above.

SUMMARY OF THE INVENTION

This is achieved by a trigger mechanism for a ball activated deviceaccording to claim 1.

In particular, a trigger mechanism for a ball activated device comprisesan inner sleeve axially slidably disposed within an outer sleeve from aninitial state wherein the ball activated device is inactive to a finalstate wherein the ball activated device is activated. A seat sleeve isaxially slidably disposed within the inner sleeve. The seat sleevecomprises radially moveable seat defining members configured to form afluid tight seal with a ball in the initial state and allowing the ballto pass in the final state. The trigger mechanism is distinguished inthat an alternating member is disposed radially moveable in a radialaperture through a wall of the inner sleeve, wherein the alternatingmember: abuts an upstream side of a first axial stopper on an innersurface of the outer sleeve and a radially exterior surface on the seatsleeve in the initial state, is received in a recess on the seat sleevein an intermediate state, and is received in a groove in the innersurface in the final state.

Thus, first the seat sleeve shifts axially within the inner sleeve inorder to align the recess on its exterior surface axially with thealternating member extending through the wall of the inner sleeve. Oncethe alternating member has entered into the recess in the seat sleeve,it may pass the first axial stopper on the inner surface of the outersleeve such that the inner sleeve can start sliding axially within theinner surface. Once the inner sleeve has moved a predetermined axialdistance within the outer sleeve so that the ball activated device isactivated, the alternating member moves radially outward into a groovein the inner surface of the outer sleeve. The predetermined axialdistance can e.g. be determined by a first complementary axial stopperdisposed upstream from the first axial stopper in the initial state.

Once the alternating member is out of the recess in the outer surface ofthe seat sleeve, the seat sleeve is permitted to proceed further withinthe inner sleeve until the seat defining members are out of the innersleeve and thereby allowed to flare out radially in order to permit theball to pass in the final state. In the final stage, the seat sleeve isprevented from leaving the inner sleeve by a second pair of axialstoppers on the seat sleeve and inner sleeve respectively.

Before and during the above series of events, the alternating member,the recess and the groove in which the alternating member is receivedare disposed between the seat sleeve and the inner surface at all times.Further, as the seat and ball needs to form a fluid tight unit in orderfor an activating pressure to build up behind the ball, well fluidscannot enter into the spaces between and behind the sleeves. In otherwords, the alternating member, recess and groove are protected from wellfluids with particles and/or well fluids causing corrosion and scaledeposits all of which might prevent or inhibit the radial motion of thealternating member.

In a preferred embodiment, the spaces between and behind the sleeves arefilled with an incompressible water-repelling fluid kept at the pressureof the surrounding well fluid. For example, the spaces within thetrigger mechanism may be filled with grease, petroleum jelly or liquidmineral oil which are contained by seals and the pressure may beequalized with bellows, membranes or piston arrangements in any knownmanner. When the fluid within the mechanism is kept at the same pressureas the surrounding well fluids, there can be no pressure difference toforce the well fluids into the spaces behind the sleeves and causeaqueous emulsions within the trigger mechanism. In particular, waterwith dissolved carbonate is prevented from entering, whereby scaling andcorrosion is prevented.

In some embodiments, the alternating member is radially biased. A biasedmember may be combined with a protrusion such as a shoulder to retain asleeve, as the bias must be overcome before the alternating member canpass the protrusion. Thus, a biased alternating member and protrusionsmay provide an alternative or supplement to shear pins and other knownretainers in the art, for example to retain the seat sleeve in theinitial state.

Some embodiments further comprise a temporary axial stopper and acomplementary member configured to temporarily halt the axial motion ofthe seat sleeve at a position wherein the alternating member can enterthe recess. Without the temporary axial stopper and complementarymember, the recess on the seat sleeve might race past the alternatingmember such that the inner sleeve would still be retained in theun-shifted position while the seat sleeve proceeds within the innersleeve and perhaps even releases the ball. If the inner sleeve remainsin the initial position, the ball activated device remains inactive.

In some embodiments, an inner surface of the seat sleeve furthercomprises key grooves configured to receive a fishing tool. In theseembodiments a fishing tool, e.g. provided on a slick line, can engagethe key grooves and be used to pull the trigger mechanism back to theinitial state.

In embodiments of the present invention, the seat defining members cancomprise axially extended collet fingers disposed in close contact witheach other around the circumference of the seat sleeve. This featureprimarily prevents particles in the well fluid from entering the spacebehind the collet fingers. For this, the term ‘close contact’ defines aspace between the fingers which is less than a predetermined minimumparticle size. In addition or alternatively the collet fingers may formpart of the fluid tight seat required to allow pressure to build upupstream from a lodged ball. Further, it should be understood that theseat defining members do not necessarily comprise collet fingers. Forexample, seat defining members arranged to slide radially in or on aguide affixed to a rigid seat sleeve might be used in other embodiments.

In some embodiments a protective sleeve may be arranged such that itextends axially from the seat sleeve over an area receiving the seatdefining members in the final state. The protective sleeve primarilyprevents debris, particles or scaling from entering or building up ingrooves or a reduced diameter into which the seat defining member aremoved in the final state in order to let the ball pass. Obviously, ifscaling or debris prevents the seat defing members from moving outward,the ball will not pass through in the final state and the triggermechanism will not work in the intended manner.

These and other features and advantages of the invention are defined inthe claims, and will become apparent from the detailed descriptionbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail using specificembodiments and with reference to the accompanying drawings in which:

FIG. 1 is a longitudinal cross section of a first embodiment in aninitial state;

FIG. 2 shows the embodiment in FIG. 1 in an intermediate state;

FIG. 3 shows the embodiment in FIG. 1 in a final state;

FIG. 4 is a detailed view of a second embodiment in the initial stateshown in FIG. 1;

FIG. 5 shows the embodiment in FIG. 4 with the seat sleeve displacedaxially;

FIG. 6 shows the embodiment in FIG. 4 in the intermediate state;

FIG. 7 shows the embodiment in FIG. 4 in the final state;

FIG. 8 is a view of a seat sleeve comprising temporary stopping means;

FIG. 9 is a section through the temporary stopping means in FIG. 8;

FIG. 10 is a longitudinal cross section of a third embodiment in aninitial state;

FIG. 11 is a perspective view of an inner sleeve shown on FIG. 10;

FIG. 12 is a perspective view of a seat sleeve shown on FIG. 10;

FIG. 13 is a perspective view of a pin shown on FIG. 10; and

FIG. 14 is a perspective view of a protective sleeve shown on FIG. 10.

DETAILED DESCRIPTION

In the description of FIGS. 1 to 3, ‘downstream’ refers to the axialdirection from top to bottom of the drawings, and ‘upstream’ refers tothe opposite direction.

FIGS. 1 to 3 show a sliding sleeve valve comprising a trigger mechanismaccording to the invention. In particular, FIG. 1 depicts a crosssectional view of a first embodiment in an initial state, FIG. 2 showsthe cross sectional view of the first embodiment in an intermediatestate and FIG. 3 the cross sectional view of the first embodiment in afinal state.

In FIG. 1, a general ball activated device 100 is represented by asliding sleeve valve comprising an outer sleeve or housing 110 includedin a tubing 200 in a conventional manner, e.g. by threaded pins andboxes. In the initial state, radial ports 105 through the walls of thehousing 110 are closed by an inner sleeve 120 having seals 127 and 128arranged around its exterior surface. The seals 127 and 128 areconfigured to engage a sealing surface forming the upstream part of aninner surface 101 within the housing 110. In FIG. 1, the seals 127 and128 are disposed upstream and downstream from the ports 105 respectivelyin order to prevent fluid from passing through the ports 105. Thesliding sleeve valve in FIG. 1 does not require a seal 129 around adownstream end of the inner sleeve 120 as long as the seals 127 and 128engage the sealing surface and prevent fluid from passing through theports 105. Thus, the element 129 might alternatively be a guide ringprovided merely to center the inner sleeve 120 within the housing 110.The ports 105, seals 127, 128 and guide element 129 are considered partsof the slide valve, and are not considered part of the trigger mechanismaccording to the invention.

In FIG. 1, a ball 300 is dropped or pumped downstream, and has not yetlanded on a ball seat formed by seat defining members 132.

An inner sleeve 120 is releasably retained within an inner surface 101by a radially moveable alternating member 125 engaging a shoulder 112 onthe inner surface 101. When released, the inner sleeve 120 is free toslide axially within the inner surface 101 until a radially extendingshoulder 122 on the inner sleeve abuts a complementary shoulder 112 onthe inner surface 101. The initial distance between shoulders 112 and122 must be sufficient to allow the upsteam edge of sleeve 120 to passthe ports 105 in order to open the slide valve, or in general toactivate the ball activated device.

A seat sleeve 130 is releasably retained within the inner sleeve 120 byshear pins 135 designed to break at a predetermined force. Whenreleased, the seat sleeve 130 is free to slide axially within the innersleeve 120 until a radially extending shoulder 133 on the seat sleeve120 abuts a complementary shoulder 123 on the inner sleeve 120. It isunderstood that the initial distance between shoulders 123 and 133 mustbe sufficient to allow the seat defing member 132 to slide out of theinner sleeve 120 such that they are no longer supported and therebyallowed to move radially outward in order to let the ball 300 passbetween the members 132 in the final state shown in FIG. 3

The trigger mechanism of the invention comprises an aperture 124extending radially through the wall of the inner sleeve 120. Thealternating member 125 is disposed in the aperture 124, and can moveradially inward or outward as it travels axially along a profile. In theinitial state in FIG. 1, the alternating member 125 is prevented frommoving radially inward by an exterior surface on the seat sleeve 130. Aslong as the alternating member 125 abuts the shoulder 112, the innersleeve is prevented from sliding axially downstream within the innersurface 101.

A recess 134 in the outer surface of the seat sleeve 130 is disposedupstream from the alternating member 125 in the initial state shown inFIG. 1. The recess 134 must be able to receive the alternating member125, at least partly, as will be described later.

In FIG. 2, a ball 300 has lodged on the ball seat within in the seatsleeve 130, and a pressure sufficient to release the seat sleeve 130from the inner sleeve 120 has been applied. In the intermediate statedepicted in FIG. 2, the seat sleeve 130 has shifted axially with respectto the inner sleeve 120, such that the alternating member 125 hasentered the recess 134. Thereby, the alternating member 125 has beenpermitted to pass the shoulder 112 and the inner sleeve 120 has startedto move axially along the inner surface 101. The inner surface 101downstream from the sealing surface and shoulder 112 prevents thealternating member 125 from moving radially outward. In this embodiment,the alternating member 125 prevents axial movement between the innersleeve 120 and the seat sleeve 130 such that the inner sleeve 120 stillprevents the seat defining members 132 from moving radially outward.

In other words, the seat defining members 132 still form a ball seat inthe intermediate state. The force exerted on the ball 300 and seatformed by the seat defing members 132 is transferred to the inner sleeve120 through the alternating member 125 such that the seat sleeve 130pulls the inner sleeve 120 downstream. Thus, in the embodimentillustrated in FIGS. 1 to 3, the recess 134 must be sufficiently deep toallow the alternating member 125 to pass within the smaller diameter ofthe inner surface 101, but not so deep that it would permit thealternating member 125 to slide along the inner surface of the innersleeve 120 rather than pulling on the inner sleeve 120. Hence, it shouldbe understood that the term ‘received in the recess’ as used in theclaim is not intended to mean that the alternating member 125 hasentered completely into the recess 134, but rather that it has enteredsufficiently to allow the alternating member to move axially within theinner surface 101 while transferring an axial force from the ball sleeve130 to the inner sleeve 120.

In FIG. 3, the inner sleeve 120 has traveled downstream along the innersurface 101 until the valve is fully open and further axial movement ofthe inner sleeve 120 along the inner surface 101 is prevented by thecomplementary shoulders 112 and 122. Once the inner sleeve has reachedits final position, the alternating member 125 is allowed to slip into agroove 114 in the inner surface 101. Now, the seat sleeve 130 is oncemore free to slide within the inner sleeve 120. As the recess 134 movesdownstream, the alternating member 125 is prevented from moving radiallyinward by an exterior surface on the seat sleeve 130 upstream from therecess 134. Thus, the alternating member 125 extends through theaperture 124 into the groove 114 and prevents the inner sleeve 120 frommoving axially within the inner surface 101. The alternating member 125and the groove 114 can replace or supplement the stopping shoulders 112and 122.

As the alternating member 125 is received in the groove 114, FIG. 3shows the seat sleeve 130 further displaced along the inner sleeve 120to a final state wherein the inner sleeve no longer supports the colletfingers 131 and permits them to flare out into a seat receiving recess115. Of course, any radially seat defining members 132 may be permittedto move radially outward once they are moved out of the inner sleeve.Thus, the invention is not limited to an embodiment having colletfingers. Further, the seat defining members 132 are radially displacedsuch that the ball 300 is permitted to pass between them in the finalstate.

In the final state shown on FIG. 3, the shoulder 133 on the seat sleeveabuts the complementary stop shoulder 123 on an interior surface of theinner sleeve 120 in the same manner as the shoulder 122 on the innersleeve abuts the complementary stop shoulder 112 on the inner surface101.

A variety of seat configurations are known to provide a fluid tight sealpermitting a pressure to build up behind a lodged ball. For example, theprior art documents U.S. Pat. No. 4,360,063 and U.S. Pat. No. 8,215,401both exhibit seats comprising collet fingers with spaces between eachfinger. In the embodiment on FIGS. 1-3, there are no spaces between thecollet fingers that large enough to allow particles, e.g. sand orproppant, to pass between the collet fingers 131. Similarly, otherembodiments of the present invention preferably are designed such thatparticles do not enter between elements of the seat sleeve. The purposeof this is to ensure that the movable elements work properly, e.g. thatthe alternating member 125 can enter the recess 134 and groove 114 inturn, and that the seat defining members 132 can expand radially intothe seat receiving area 115.

In general, the design must be adapted to the operation at hand. Forexample, a trigger mechanism according to the invention designed for acementing or fracturing operation would advantageously be designed suchthat particles of the sizes involved do not pass between the elements ofthe seat sleeve 130 under the pressures employed during the operation.

From the above discussion of FIGS. 1 to 3 it should be understood thatthe alternating member 125 preferably is protected between the innersurface 101 and the seat sleeve 130 at all times before and during theactivation procedure. Thus, particles such as sand or proppant cannotjeopardize the operation of the trigger mechanism even during cementingor fracturing operations involving high pressures.

In a preferred embodiment, the spaces between and behind the sleeves,including the aperture 124 and groove 114, are filled with filled withan incompressible, water-repelling fluid kept at the pressure of thesurrounding well fluid.

Seals between the sleeves are omitted from the figures for clarity.However, it is understood that conventional seals similar to the seals127, 128 of the ball activated device, for example O-rings supported ina conventional manner, must be provided to ensure a fluid tightconnection such that a pressure may be built up behind the ball 300.Conversely, if fluid was allowed to pass through or between the sleeves,a pressure could not build up in order to exert an axial force on thelodged ball. It is considered within the capabilities of the skilledperson to provide seals suitable for this purpose as well as anyadditional seals required for keeping a clean, incompressible fluidwithin the spaces behind and between the sleeves. In particular, liquidfilled spaces prevent particles and water containing dissolvedcarbonates from entering, and thereby prevent deposits of particlesand/or scaling from forming. When water influx is inhibited orprevented, corrosion is also inhibited or prevented.

Suitable incompressible fluids are water-repelling liquids such asgrease, petroleum jelly or mineral oil. The specific carbon numbers willdepend on the expected pressure and temperature in the well. In additionto prevent liquid from escaping from the spaces within the triggermechanism, the seals prevent well fluids from entering into the spaces.

Pressure equalizers are advantageously provided to minimize the pressuredifference, and hence the driving force, from the ambient well fluid tothe interior of the trigger mechanism. For example, a bellow, membraneor piston might be provided to equalize the pressure within the triggermechanism with the ambient pressure in the well. Such pressureequalizers are known in the art, and are not described further herein.

In the embodiment with collet fingers 131 illustrated in FIGS. 1-3, thefingers 131 are arranged in close contact with each other around thecircumference of the seat sleeve. As discussed above, the contact shouldbe close enough to prevent a particle with a predetermined minimum sizefrom passing between them under the pressures involved in the operationat hand. The contacts between the fingers can advantageulsy also befluid tight, so that the fingers are integral parts of the pressuretight structure required for exerting a force on the lodged ball.

In a still further preferred embodiment, a protective sleeve 150 extendsaxially from the downstream end of the seat sleeve to a downstream partof the tubing 200. In the initial state on FIG. 1, the protective sleeve150 would thus extend over the entire seat receiving are 115. The spacebehind the protective sleeve 150 is advantageously filled with anincompressible water-repelling fluid in order to prevent particledeposits, scaling and corrosion as discussed above.

FIGS. 4 to 7 are enlarged, partial views of a second embodiment of theinvention in which only one side of the trigger mechanism is shown. Thedownstream direction is from left to right.

FIG. 4 illustrates an alternative embodiment of a trigger mechanismaccording to the invention in the initial state corresponding to theinitial state illustrated in FIG. 1. In FIG. 4, the alternating memberis depicted as a roller 126, i.e. a cylinder or a ball. The roller 126is biased radially inward as illustrated by the arrow F. The bias can beprovided in known manner, e.g. by a disc spring, a leaf spring or acompression spring and is not discussed further herein.

In FIG. 4, the roller 126 abuts the shoulder 112 and prevents the innersleeve 120 from moving downstream relative to the inner surface 120. Aradially exterior surface of the seat sleeve 130 prevents the roller 126from moving inward. This corresponds to the initial state described inconnection with FIG. 1. In addition, an initial state holding shoulder133 on the exterior surface of the seat sleeve 130 abuts the roller 126on its upstream side. The bias force F must be overcome before theroller 126 can pass the shoulder 133 so that the seat sleeve 130 canslide axially downstream within the inner sleeve 120. The inclination ofthe shoulder 133 and size of the biasing force F are adapted to preventthe seat sleeve 130 from moving within the inner sleeve 120 before apredetermined force is applied. Thus, the bias force F and shoulder 133could be adapted in order to replace the shear pins 135 in FIG. 1.

FIG. 5 illustrates a state shortly after the predetermined force isexerted on the ball. In this state, the roller 126 has been forcedradially outward against the biasing force F and is disposed between anexterior surface on the seat sleeve 130 and the inner surface 101 of theouter sleeve 110 such that the seat sleeve 130 is permitted to slidedownstream within the inner sleeve 120. The roller 126 still abuts theshoulder 112 on the inner surface 101 and is still prevented from movingradially inward by an exterrior surface on the seat sleeve 130, so theinner sleeve 120 is still not free to slide axially downstream withinthe inner surface 101.

In FIG. 6, the roller 126 is received in the recess 134 on the seatsleeve 130 so that the roller 126 no longer abuts the stopping shoulder112 on the inner surface 101. Thereby, the inner sleeve 120 is allowedto slide downstream within the inner surface 101. The state illustratedin FIG. 6 corresponds to the intermediate state shown in FIG. 2.

In FIG. 7, the roller 126 is received in the groove 114 and prevents theinner sleeve 120 from moving downstream relative to the inner surface120. A radially exterior surface of the seat sleeve 130 prevents theroller 126 from moving inward. This corresponds to the final statedescribed in connection with FIG. 3. In addition, a final state holdingshoulder 137 on the exterior surface of the seat sleeve 130 abuts theroller 126 on its upstream side. The roller 126 cannot move radiallyoutward, and hence it cannot pass the shoulder 137. Thus, the roller 126and shoulder 137 is an alternative stopping mechanism that mightsupplement or replace the shoulders 123 and 133 in FIG. 3.

FIGS. 8 and 9 illustrate temporary stopping means comprising apin-in-groove arrangement.

FIG. 8 is a side view of the seat sleeve 130 in FIGS. 1-3. Assume thatan alternating member such as a lug 125 or roller 126 abuts the shoulder133 in the initial state as depicted in FIG. 4. When the seat sleeve isreleased and has traveled a predetermined length L within the innersleeve, the alternating member 125, 126 should enter into the externalrecess 134 on the seat sleeve 130 as shown in FIGS. 2 and 6. Now, if theseat sleeve 130 moves too fast relative to the inner sleeve 120, thealternating member 125, 126 might skip past the recess 134 withoutentering. If this happens, the seat sleeve 130 would continue out of theinner sleeve and perhaps release the drop ball 300, while the innersleeve 120 remains unshifted within the inner surface 101. That is, thetrigger mechanism fails if the alternating member 125, 126 does notenter the recess 134 when the seat sleeve is shifted the distance Ldownstream from its initial position relative to the inner sleeve 120.

To ensure that the alternating member 125, 126 enters into the recess134 at a predetermined displacement L, a pin 1250 connected to the innersleeve 120 is axially slidably disposed in a longitudinal groove 138 onthe seat sleeve 130. In the initial position shown on FIG. 8, the pin1250 is at the downstream end of the longitudinal groove 138. Aninclined shoulder 1380 (FIG. 9) is arranged a distance L upstream in thegroove 138. Thus, the length L of the longitudinal groove 138corrresponds to the length L the alternating member 125, 126 travelsfrom the initial state to the recess 134. Obviously, the longitudinalgroove 138 might be arranged anywhere on the seat sleeve 130 with acomplementary pin on the inner sleeve 120. Alternatively, a longitudinalgroove on the inner sleeve 120 with a pin on the seat sleeve 130 wouldwork in the same manner.

FIG. 9 is a sectional view of the recess 138 in FIG. 8 and thecorresponding part of an inner sleeve 120 comprising the pin 1250. Forthis illustration, it is assumed that the pin 1250 is an integral partof an arm 1200 cut out of the inner sleeve 120 and then bent into thelongitudinal groove 138 in the seat sleeve 130. An inclined surface 1380is disposed a distance L from the pin 1250. The distance L in FIG. 9equals the distance L in FIG. 8. However, the scales are different sothe distance L seems longer in FIG. 9.

When the seat sleeve 130 is displaced nearly a distance L downstream,i.e. toward the right in FIG. 9, relative to the inner sleeve 120, thepin 1250 engages the inclined surface 1380. Further displacement of theseat sleeve 130 causes the pin 1250 to climb up the inclined surface1380 until the arm 1200 is bent back to a near horizontal position. Thisclimbing causes the seat sleeve 130 to slow down momentarily relative tothe inner sleeve 120 shortly before and after the pin 1250 has traveleda distance L in the longitudinal groove 138. As the length L correspondsto when the alternating member 125, 126 passes the recess 134 on FIG. 8,the temporary axial stopper 1380 in the longitudinal groove 138 and thecorresponding member 1250 on the inner sleeve 120 are easily adapted toensure that the alternating member 125, 126 enters properly into therecess 134.

Generally, any radially protruding element on a first sleeve engaging acomplemetary member on a second sleeve could stop the relative axialmovement between the first and second sleeves. In the claims, the terms‘axial stopper’ and ‘complementary member’ denotes one such pair ofelements designed to prevent or inhibit motion between two sleeves. Inthe description above, stopping shoulders 112, 122 and 123, 133;shoulders 133, 137 agains roller 126; alternating member 125 in groove114 and pin 1250 in longitudinal groove 138 are examples of such pairs.Further varieties, e.g. providing the groove 138 on the inner sleeve 120and the pin 1250 on the seat sleeve 130, are considered obvious. Apractical design of axial stoppers and complementary members is left tothe skilled person.

In the drawings, some recesses and grooves are depicted without inclinedshoulders to illustrate the invention as clearly as possible, i.e.without unnecessary details. However, the recesses or grooves can beprovided with inclined surfaces to facilitate entry and/or exit of acomplementary member such as the lug 125 or roller 126 described above.In particular, it is noted that the activating sequence shown in FIGS. 1to 3 can be reversed if the seat sleeve 130 is pulled back from thefinal position in FIG. 3 to the initial position in FIG. 1. For this,inclined surfaces at both axial ends of the recesses and grooves wouldbe advantageous. Further, the shear pins 135 should be replaced by analternative release mechanism such as the one shown on FIGS. 4 and 5 forsuch an application. In order to reset the ball activated device 100, aninner surface of the seat sleeve could comprise key grooves to receive aconventional fishing tool, for example deployed on a slick line.

Next, assume that the ball activated device 100 in FIG. 1 is left in awell for an extended period of time. As discussed, the alternatingmember 125, 126 is protected behind the seat sleeve 130. A protectivesleeve 150 extending axially from the downstream end of the seat sleeve130 protects the annulus or seat receiving area 115 provided for thecollet finger 131 and radially expanding seat defining members 132 inthe final state shown in FIG. 3. However, corrosion, scaling and otherdeposits may still build up during the extended period and cause theparts to stick to each other or otherwise prevent the parts from movingrelative to each other.

According to the present invention, the different parts are released insequence rather than all at once. First, the friction forces stickingthe seat sleeve 130 to the inner surface 120 (plus the force required tobreak the shear pins 135 in FIG. 1 or overcome the bias F in FIG. 4)must be overcome. A force required to tear loose the inner sleeve 120 isnot required at this stage.

When the seat sleeve 130 has shifted downstream a distance L within theinner sleeve 120 as depicted on FIGS. 8 and 9, it has built up a certainspeed and and is suddenly stopped because the alternating member 125,126 enters into recess 134 and/or because a complementary member 1250hits a temporary axial stopper 1380. The resulting sudden jar might helploosening any bonds between the inner sleeve 120 and the inner surface101 in which it slides, even if the inner sleeve 120 is not permitted toslide within the inner surface 101 before the alternating member 125,126 is properly received in the external recess 134 on the seat sleeve130.

For trigger mechanisms designed to stay in a well for an extended periodof time, it might be advantageous to make the area of the seat sleeve130 exposed to the well fluids small compared to the exposed area of theinner sleeve 120 and also in comparison to the exposed area of anoptional protecting sleeve 150, because a smaller exposed area decreasesthe amount of deposits that might cause the seat sleeve 130 to stick.The area of the seat sleeve can, for example, be decreased by using pinson the seat sleeve 130 and longitudinal grooves on the inner sleeve asaxial stoppers/complementary members. Also, the collet fingers 131 andmembers 132 shown in FIGS. 1 to 3 could be replaced with other seatdefining members 132 configured to move radially outward once they areout of the inner sleeve 120. For example, the seat defining members 132coud be slidably disposed on radial guides (not shown) arrangedperpendicular to the central axis of the seat sleeve 130. Further, themass of the seat sleeve 130 may be increased to improve the jarringeffect.

FIG. 10 shows an alternative embodiment of the trigger mechanism 100 inthe initial state, i.e. the state shown on FIG. 1. Reference numerals100-200 correspond to those on FIG. 1, and are discussed above. Thedifferences from FIG. 1 will be explained in the next paragraphs.

The alternating member 125 in FIG. 10 is mounted on an arm, and may becut out of the inner sleeve 120 by providing the aperture 124 alongthree edges of the alternating member 125 as shown on FIG. 10.

On FIG. 10, holes 1150 are provided for shear pins attaching the innersleeve 120 to the inner surface 101 of the outer sleeve 110 in theinitial state. The shear pins (not shown) retain the inner sleeve 120 inthe outer sleeve 110 until a force sufficient to break them is exertedon the ball and seat.

Pins 433 sliding in longitudinal grooves 423 provide an alternativemeans for limiting the relative motion between the inner sleeve 120 andthe seat sleeve 130. That is, the pins 433 in the grooves 423 serve thesame purpose as the shoulders 123 and 133 on FIG. 1. The holes 4330 inthe seat sleeve 130 are provided for attaching the pins 433.

Similar pins 1250 in grooves 138 stops the axial motion of the seatsleeve 130 within the inner sleeve 130 temporarily to ensure that thealternating member 125 enters the groove 134 properly as discussed inconnection with FIGS. 8 and 9 above. In contrast to the embodiment onFIG. 9, which merely slows the relative motion when the pin 1250 hitsthe inclination 1380, the pin 1250 on FIG. 13 is prevented from movingoutward through the hole 1251 in sleeve 120 by the inner surface 101.Thus, the pin 1250 stops the relative motion between the inner sleeve120 and the seat sleeve 130 when it hits the upstream end 1380 of thegroove 138. Referring to the discussion above, the pin 1250 is allowedto travel a longitudinal distance L (not shown on FIG. 10) along groove138 before it hits the upstream end 1380 of grove 138. This length Lcorresponds to the length which the alternating member 125 must slidealong sleeve 130 before it enters groove 134. The pin 1250 on FIG. 13 ispermitted to move radially outward once it is aligned with the recess114 later on in the activation sequence, and thus halts the relativemotion between sleeves 120 and 130 from it abuts the end 1380 of groove138 until it enters into groove 114. In other words, the pin 1250 haltsthe relative motion of the seat sleeve 130 within the inner sleeve 120temporarily.

An optional leaf spring 435 is shown on FIG. 10, where it retains theseat sleeve 130 within the inner sleeve 120 in the initial state. Alongitudinal force exerted on the seat sleeve 130 causes the spring 435to move radially inwards until the seat sleeve 130 is free to traveldownstream within the inner sleeve 120. The leaf spring 435 may serve asan alternative retainer to the shear pins 135 on FIG. 1.

In the initial state on FIG. 10, the seat defining members 132 areprevented from flaring out by a portion 420 of the inner surface of theinner sleeve 120. The length of the portion 420 is sufficient to preventradial motion of the seat defining members 132 when the seat sleeve 130has shifted downstream relative to the inner sleeve 120 such that thealternating member 125 is received in groove 134, i.e. when the triggermechanism is in an intermediate state corresponding to the state shownon FIG. 2.

On FIG. 10, the fingers 131 are provided with a frustoconical portion1310. The upstream and largest diameter of the portion 1310 issubstantially equal to the outer diameter of the seat defining members132, while the lower end of the frustoconical portion 1310 has a reduceddiameter. The length of the portion 1310 corresponds to the length thatthe pins 433 can travel in the grooves 423. In the final position, theportion 1310 lies along the inner portion 420, and the seat definingmembers 132 have moved radially out into the seat receiving recess 115in order to permit the ball to pass as in FIG. 3. Thus, thefrustoconical portion 1310 must be longer than the length of the portion420 within the inner sleeve 120.

In addition to guide(s) 129 centering the inner sleeve 120 within theinner surface 110, a seal 429 is provided in the embodiment on FIG. 10.The seal 429 covers the groove 114 in the initial state, such that waterand/or particles do not enter the groove 114 and cause scaling ordeposits as discussed above.

The distal or downstream ends of the collet fingers 131 interlock withthe upstream end of the protective sleeve 150 in a castellation 140. Thecastellation 140 prevents relative rotation between the seat sleeve 130and the protective sleeve 150, and permits the seat defining members 132to flare outward into the seat receiving recess 115 when the triggermechanism 100 reaches its final state.

FIG. 11 is a perspective view of the inner sleeve 120 on FIG. 10.Annular grooves 1270 and 1280 are provided for receiving the seals 127and 128, respectively. The alternating members 125 and holes 1150 forattaching shear pins are described above. The holes 1251 through thewalls of the sleeve are provided for pins 1250 as discussed inconnection with FIG. 13. An annular groove 1290 is provided for a guide129 and an annular groove 4290 for the seal 429 described in connectionwith FIG. 10.

FIG. 12 is a perspective view of the seat sleeve 130 on FIG. 10, andshows an annular recess 139 in addition to the elements shown on FIG. 10and described above. The annular recess 139 is provided to receive aseal (not shown) between the seat sleeve 130 and the inner sleeve 120such that a pressure can be built behind a ball lodged on the seat.

FIG. 13 shows a pin 1250 with a frustoconical end 1252. The largerdiameter of the pin 1250 fits into a hole 1251 through the wall of theinner sleeve 120, cf. FIG. 11. The frustoconical end 1252 fits into thelongitudinal groove 138, and may travel a distance L along the groove138 from the downstream end to the upstream end 1380. The axial lengthof the pin 1250 corresponds to the distance between the exterior surfaceof the inner sleeve 120 and the bottom of groove 138. Thus, when theseat sleeve 130 has shifted axially the distance L with respect to theinner sleeve 120, the frustoconical end 1252 hits the upstream end 1380of groove 138 and remains in contact with the end 1380 until it isaligned with the groove 114 in the outer sleeve 110, causing a temporaryhalt in the relative motion between the inner sleeve 120 and the seatsleeve 130 as described above. As above, the distance L corresponds tothe axial shift required for the alternating members 125 to align withthe grooves 134, and the temporary halt ensures that the alternatingmembers 125 enter the grooves 134. After the temporary halt, thefrustoconical end 1250 causes the pin 1250 to move out of the groove 138and radially outward in the hole 1251 through the inner sleeve 120 andinto the recess 114 in the outer sleeve. The holes 1251 are shown onFIG. 11, and the assembly with recess 114 and pins 1250 through the wallof the inner sleeve 120 appears on FIG. 10.

The means on FIGS. 8 and 9 and the end 1380 of groove 138 and pin 1250on FIGS. 12 and 13 are both examples of a separate axial stopper 1380 onthe seat sleeve 130 and a complementary member 1250 configured totemporarily halt the axial motion of the seat sleeve 130 at a positionwherein the alternating member 125, 126 can enter the recess 134.

When the pins 1250 shown on FIGS. 10 and 13 are received in the recess114, the seat sleeve 130 is free to move axially within the inner sleeve120 until stoppers 433 attached to the holes 4330 reaches the end ofgrooves 423 in the inner sleeve as described in connection with FIG. 10.

FIG. 14 shows a protective sleeve 150 with a castellation 140 adapted tofit into a similarly shaped downstream end of the seat sleeve 130. Thecastellation 140 prevents relative rotation between the seat sleeve 130and the protective sleeve 150

Various other embodiments of the invention will be apparent to thoseskilled in the art reading the description above. However, the inventionis not limited to the specific exemplary embodiments above, but isdefined by the subject matter set forth in the appended claims.

1. A trigger mechanism for a ball activated device, the triggermechanism comprising: an inner sleeve axially slidably disposed withinan outer sleeve from an initial state wherein the ball activated deviceis inactive to a final state wherein the ball activated device isactivated; a seat sleeve axially slidably disposed within the innersleeve, the seat sleeve comprising radially moveable seat definingmembers configured to form a fluid tight seal with a ball in the initialstate and allowing the ball to pass in the final state; and analternating member is disposed radially moveably in a radial aperturethrough a wall of the inner sleeve, wherein the alternating member:abuts an upstream side of a first axial stopper on an inner surface ofthe outer sleeve and a radially exterior surface on the seat sleeve inthe initial state, is received in a recess on the seat sleeve in anintermediate state, and is received in a groove in the inner surface inthe final state.
 2. The trigger mechanism of claim 1 wherein the spacesbetween and behind the sleeves are filled with an incompressible,water-repelling fluid kept at the pressure of the ambient well fluid. 3.The trigger mechanism of claim 1 wherein the alternating member isradially biased.
 4. The trigger mechanism of claim 3 wherein the seatsleeve is retained by the alternating member and an initial stateholding shoulder on the seat sleeve in the initial state.
 5. The triggermechanism of claim 1 wherein the seat sleeve is retained by thealternating member and a final state holding shoulder on the seat sleevein the final state.
 6. The trigger mechanism of claim 1 furthercomprising a separate axial stopper on the seat sleeve and acomplementary member configured to temporarily halt the axial motion ofthe seat sleeve at a position wherein the alternating member can enterthe recess.
 7. The trigger mechanism of claim 1 wherein an inner surfaceof the seat sleeve further comprises key grooves configured to receive afishing tool.
 8. The trigger mechanism of claim 1 wherein the seatdefining members comprise axially extending collet fingers disposed inclose contact with each other around the circumference of the seatsleeve.
 9. The trigger mechanism of any claim 1 wherein the seatdefining members are slidably mounted on guides oriented radially andperpendicular to a central axis of the seat sleeve.
 10. The triggermechanism of claim 1 further comprising a protective sleeve extendingaxially from the seat sleeve over a seat receiving area in the initialstate, the protective sleeve permitting the seat defining members toenter into the seat receiving area in the final state.